ASR-33 differences

tony duell ard at
Wed Aug 26 13:03:33 CDT 2015

> I've finally gotten a hold of a restored ASR-33.  One question I have
> concerns the paper tape reader.
> My recollection of using this TTY in the 70's was that the reader switch
> lever had 4 positions; on this tty there are 3.  I know that for I have to
> add a reader control relay to interface to my PDP-8.

I've only ever seen the ones with 3 position levers, but from reading the 
manuals I think the 3 position levers are manual control models and
4 position levers are automatic control models (with extra levers and
swtiches in the stunt box to start and stop the reader using XON/XOFF

> So the question is: does having the 3 vs. 4 position reader lever affect
> using this with a PDP-8?

The 3 position lever models (manual control) can certainly take the reader
run relay and be used with PDP8s and PDP11s. 


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